The NYSCF First Annual Translational Stem Cell Research Conference

Web Sites

The New York Stem Cell Foundation
The sponsor of the First Translational Stem Cell Research Conference is a nonprofit organization organized to support scientists engaged in stem cell research, to educate the public about the importance and potential benefits of the field, and to establish research facilities supported by private funding. They are planning their second annual conference for October 15-16, 2007.

Beta Cell Biology Consortium
An interdisciplinary team of researchers working to advance our understanding of pancreatic islet development and function with the long-term goal of developing a cell-based therapy for insulin delivery.

California Institute for Regenerative Medicine
Governed by the Independent Citizens Oversight Committee, CIRM was established in 2004 with the passage of Proposition 71, the California Stem Cell Research and Cures Initiative. The statewide ballot measure, which provided $3 billion in funding for stem cell research at California universities and research institutions, was approved by California voters, and called for the establishment of an entity to make grants and provide loans for stem cell research, research facilities, and other vital research opportunities.

European Consortium for Stem Cell Research
EuroStemCell, is an Integrated Project of the European Union's Sixth Framework Programme. The goal of the 4-year project is to develop an advanced technological platform for new cell based therapies and create a foundation for translational research in the stem cell field. The project draws together the capabilities of 11 academic centres and 3 SMEs in 8 European countries, with expertise encompassing transgenesis, stem cell biology, developmental biology, tissue repair, in vivo disease models and clinical cell transplantation. The key aim is to develop well-characterized cell lines of therapeutic potential derived from stem cells of embryonic, neural, mesodermal and epithelial origin.

International Society for Stem Cell Research
From a society promoting the exchange of information on stem cell research, this site provides a wide variety of resources, including a glossary of terms, a list of relevant meetings, and information for the general public. Includes a listing of human embryonic stem cell lines, with links and protocols.

International Stem Cell Forum (ISCF)
The ISCF is made up of 14 funders of stem cell research from around the world. It was founded in January 2003 to encourage international collaboration and funding support for stem cell research.

Juvenile Diabetes Research Foundation
JDRF is the leading charitable funder and advocate of type 1 (juvenile) diabetes research worldwide. The mission of JDRF is to find a cure for diabetes and its complications through the support of research. Their site contains information about stem cell research for treating diabetes.

The Stem Cell Database
A joint project of the laboratories of Ihor R. Lemischka and Kateri A. Moore (Princeton University) and Christian Stoeckert (University of Pennsylvania), this site serves as a catalog of the genes involved in blood cell production originating from multipotent, self-renewing hematopoietic stem cells.

Journal Articles

Kevin Eggan

Eggan K, Baldwin K, Tackett M, et al. 2004. Mice cloned from olfactory sensory neurons. Nature 428: 44-49.

Eggan K, Jaenisch R. 2003. Micromanipulating dosage compensation: understanding X-chromosome inactivation through nuclear transplantation. Semin. Cell Dev. Biol. 14: 349-358.

Eggan K, Jurga S, Gosden R. 2006. Ovulated oocytes in adult mice derive from non-circulating germ cells. Nature 441: 1109-1114.

Geijsen N, Horoschak M, Kim K, et al. 2004. Derivation of embryonic germ cells and male gametes from embryonic stem cells. Nature 427: 148-154.

Jaenisch R, Hochedlinger K, Blelloch R et al. 2004. Nuclear cloning, epigenetic reprogramming, and cellular differentiation. Cold Spring Harb. Symp. Quant. Biol. 69: 19-27.

Takahashi K, Yamanaka S. 2006. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 126: 663-676.

Renee Reijo Pera

Ezeh UI, Turek PJ, Reijo RA, Clark AT. 2005. Human embryonic stem cell genes OCT4, NANOG, STELLAR, and GDF3 are expressed in both seminoma and breast carcinoma. Cancer 104: 2255-2265.

Kostiner DR, Turek, PJ, Reijo RA.1998. Male infertility: analysis of the markers and genes on the human Y chromosome. Hum. Reprod. 13: 3032-3038. (PDF, 119 KB) Full Text

Looijenga LH, Hermus R, Gillis AJ, et al. 2006. Genomic and expression profiling of human spermatocytic seminomas: primary spermatocyte as tumorigenic precursor and DMRT1 as candidate chromosome 9 gene. Cancer Res. 66: 290-302. Full Text

Mulhall JP, Reijo R, Alagappan R, et al. 1997. Azoospermic men with deletion of the DAZ gene cluster are capable of completing spermatogenesis: fertilization, normal embryonic development and pregnancy occur when retrieved testicular spermatozoa are used for intracytoplasmic sperm injection. Hum. Reprod. 12: 503-508. (PDF, 148 KB) Full Text

Nudell D, Castillo M, Turek PJ, Pera RR. 2000. Increased frequency of mutations in DNA from infertile men with meiotic arrest. Hum. Reprod. 15: 1289-1294. Full Text

Reijo RA, Dorfman DM, Slee R, et al. 2000. DAZ family proteins exist throughout male germ cell development and transit from nucleus to cytoplasm at meiosis in humans and mice. Biol. Reprod. 63: 1490-1496. Full Text

Saxena R, Brown LG, Hawkins T, et al. 1996. The DAZ gene cluster on the human Y chromosome arose from an autosomal gene that was transposed, repeatedly amplified and pruned. Nat. Genet. 14: 292-299.

Ali Brivanlou

Amit M, Itskovitz-Eldor J. 2006. Sources, derivation, and culture of human embryonic stem cells. Semin. Reprod. Med. 24: 298-303.

James D, Noggle SA, Swigut T, Brivanlou AH. 2006. Contribution of human embryonic stem cells to mouse blastocysts. Dev. Biol. 295: 90-102.

Levine AJ, Brivanlou AH. 2006. GDF3, a BMP inhibitor, regulates cell fate in stem cells and early embryos. Development 133: 209-216. Full Text

Noggle SA, James D, Brivanlou AH. 2005. A molecular basis for human embryonic stem cell pluripotency. Stem Cell Rev. 1: 111-118.

Sato N, Brivanlou AH. 2006. Manipulation of self-renewal in human embryonic stem cells through a novel pharmacological GSK-3 inhibitor. Methods Mol. Biol. 331: 115-128.

Sato N, Brivanlou AH. 2006. Microarray approach to identify the signaling network responsible for self-renewal of human embryonic stem cells. Methods Mol. Biol. 331: 267-283.

Sato N, Meijer L, Skaltsounis L, et al. 2004. Maintenance of pluripotency in human and mouse embryonic stem cells through activation of Wnt signaling by a pharmacological GSK-3-specific inhibitor. Nat. Med. 10: 55-63.

Spagnoli FM, Brivanlou AH. 2005. A full menu for stem-cell research. Genome Biol. 6: 311.

Alison Murdoch

Campbell KH, McWhir J, Ritchie WA, Wilmut I. 1996. Sheep cloned by nuclear transfer from a cultured cell line. Nature 380: 64-66.

Choudhary M, Nesbitt M, Leary C, Murdoch AP. 2006. Donation of fresh oocytes for nuclear transfer research—a new approach. Reprod. Biomed. Online 13: 301-302.

Hall VJ, Compton D, Stojkovic P, et al. 2007. Developmental competence of human in vitro aged oocytes as host cells for nuclear transfer. Hum. Reprod. 22: 52-62.

Herbert M, Levasseur M, Homer H, et al. 2003. Homologue disjunction in mouse oocytes requires proteolysis of securin and cyclin B1. Nat. Cell Biol. 5: 1023-1025.

Lavoir MC, Weier J, Conaghan J, Pedersen RA. 2005. Poor development of human nuclear transfer embryos using failed fertilized oocytes. Reprod. Biomed. Online 11: 740-744.

Ozil JP, Huneau D. 2001. Activation of rabbit oocytes: the impact of the Ca2⁺ signal regime on development. Development 128: 917-928. (PDF, 310 KB) Full Text

Stojkovic M, Stojkovic P, Leary C, et al. 2005. Derivation of a human blastocyst after heterologous nuclear transfer to donated oocytes. Reprod. Biomed. Online 11: 226-231.

Gordon Keller

Gadue P, Huber TL, Paddison PJ, Keller GM. 2006. Wnt and TGF-beta signaling are required for the induction of an in vitro model of primitive streak formation using embryonic stem cells. Proc. Nat. Acad. Sci. USA 103: 16806-16811.

Germano IM, Uzzaman M, Beneviste RJ, et al. 2006. Apoptosis in human glioblastoma cells produced using embryonic stem cell-derived astrocytes expressing tumor necrosis factor-related apoptosis-inducing ligand. J. Neurosurg. 105: 88-95.

Gouon-Evans, Boussemart L, Gadue P, et al. 2006. BMP-4 is required for hepatic specification of mouse embryonic stem cell-derived definitive endoderm. Nat. Biotechnol. 24: 1402-1411.

Kattman SJ, Huber TL, Keller GM. 2006. Multipotent flk-1⁺ cardiovascular progenitor cells give rise to the cardiomyocyte, endothelial, and vascular smooth muscle lineages. Dev. Cell 11: 723-732.

Kennedy M, D'Souza SL, Lynch-Kattman M, et al. 2006. Development of the hemangioblast defines the onset of hematopoiesis in human ES cell differentiation cultures. Blood Dec. 5; [Epub ahead of print]

Zafonte BT, Liu S, Lynch-Kattman M, et al. 2007. Smad1 expands the hemangioblast population within a limited developmental window. Blood 109: 516-523.

Domenico Accili

Buteau J, Shlien A, Foisy S, Accili D. 2007. Metabolic diapause in pancreatic beta-cells expressing a gain-of-function mutant of the forkhead protein Foxo1. J. Biol. Chem. 282: 287-293.

Buteau J, Spatz ML, Accili D. 2006. Transcription factor FoxO1 mediates glucagon-like peptide-1 effects on pancreatic beta-cell mass. Diabetes 55: 1190-1196. Full Text

Matsumoto M, Han S, Kitamura T, Accili D. 2006. Dual role of transcription factor FoxO1 in controlling hepatic insulin sensitivity and lipid metabolism. J. Clin. Invest. 116: 2464-2472. Full Text

Okamoto H, Hribal ML, Lin HV, et al. 2006. Role of the forkhead protein FoxO1 in beta cell compensation to insulin resistance. J. Clin. Invest. 116: 775-782. Full Text

Allen M. Spiegel

Schnepp RW, Chen YX, Wang H. 2006. Mutation of tumor suppressor gene Men1 acutely enhances proliferation of pancreatic islet cells. Cancer Res. 66: 5707-5715.

Tayaramma T, Ma B, Rhode M, Mayer H. 2006. Chromatin-remodeling factors allow differentiation of bone marrow cells into insulin-producing cells. Stem Cells 24: 2858-2867.

Xu X, Kahan B, Forgianni A, et al. 2006. Endoderm and pancreatic islet lineage differentiation from human embryonic stem cells. Cloning Stem Cells 8: 96-107.

Zalzman M, Anker-Kitai L, Efrat S. 2005. Differentiation of human liver-derived, insulin-producing cells toward the β-cell phenotype. Diabetes 54: 2568-2575. Full Text

Anthony Atala

De Coppi P, Bartsch G Jr, Siddiqui MM, et al. 2007. Isolation of amniotic stem cell lines with potential for therapy. Nat. Biotechnol. 25: 100-106.

De Coppi P, Callegari A, Chiavegato A, et al. 2007. Amniotic fluid and bone marrow derived mesenchymal stem cells can be converted to smooth muscle cells in the cryo-injured rat bladder and prevent compensatory hypertrophy of surviving smooth muscle cells. J. Urol. 177: 369-376.

Delo DM, DeCoppi P, Bartsch, G Jr, Atala A. 2006. Amniotic fluid and placental stem cells. Methods Enzymol. 419: 426-438.

Eberli D, Atala A. 2006. Tissue engineering using adult stem cells. Methods Enzymol. 420: 287-302.

Hipp J, Atala A. 2006. GeneChips in stem cell research. Methods Enzymol. 420: 162-224.

Yu Y, Fuhr J, Boye E, et al. 2006. Mesenchymal stem cells and adipogenesis in hemangioma involution. Stem Cells 24: 1605-1612.

Douglas Melton

Boyer LA, Lee TI, Cole MF, et al. 2005. Core transcriptional regulatory circuitry in human embryonic stem cells. Cell 122: 947-956.

Cowan CA, Atienza J, Melton DA, Eggan K. 2005. Nuclear reprogramming of somatic cells after fusion with human embryonic stem cells. Science 309: 1369-1373.

Dor Y, Brown J, Martinez OI, Melton DA. 2004. Adult pancreatic beta-cells are formed by self-duplication rather than stem-cell differentiation. Nature 429:41-46.

Greenwood AL, Li S, Jones K, Melton DA. 2007. Notch signaling reveals developmental plasticity of Pax4⁺ pancreatic endocrine progenitors and shunts them to a duct fate. Mech. Dev. 124: 97-107.

Lee TI, Jenner RG, Boyer LA, et al. 2006. Control of developmental regulators by Polycomb in human embryonic stem cells. Cell 125: 301-313.

Melton DA. 2006. Reversal of type 1 diabetes in mice. N. Engl. J. Med. 355: 89-90.

Nikolova G, Jabs N, Konstantinova I, et al. 2006. The vascular basement membrane: a niche for insulin gene expression and Beta cell proliferation. Dev. Cell 10: 397-405.

Murtaugh LC, Law AC, Dor Y, Melton DA. 2005. Beta-catenin is essential for pancreatic acinar but not islet development. Development 132: 4663-4674.

Shaywitz DA, Melton DA. 2005. The molecular biography of the cell. Cell 120: 729-731.

Stanger BZ, Datar R, Murtaugh LC, Melton DA. 2005. Direct regulation of intestinal fate by Notch. Proc. Natl. Acad. Sci. USA 102: 12443-12448. Full Text

Stanger BZ, Stiles B, Lauwers GY, et al. 2005. Pten constrains centroacinar cell expansion and malignant transformation in the pancreas. Cancer Cell 8: 185-195.

Stanger BZ, Tanaka AJ, Melton DA. 2007. Organ size is limited by the number of embryonic progenitor cells in the pancreas but not the liver. Nature Jan 28; [Epub ahead of print]

John Gearhart

Faden RR, Dawson L, Bateman-House AS, et al. 2003. Public stem cell banks: considerations of justice in stem cell research and therapy. Hastings Cent. Rep. 33: 13-27.

Frimberger D, Morales N, Gearhart JD, et al. 2006. Human embryoid body-derived stem cells in tissue engineering-enhanced migration in co-culture with bladder smooth muscle and urothelium. Urology 67: 1298-1303.

Jansen JF, Shamblott MJ, van Zijl PC, et al. 2006. Stem cell profiling by nuclear magnetic resonance spectroscopy. Magn. Reson. Med. 56: 666-670.

Kerr CL, Shamblott MJ, Gearhart JD. 2006. Pluripotent stem cells from germ cells. Methods Enzymol. 419: 400-426.

Kerr CL, Gearhart JD, Elliott AM, Donovan PJ. 2006. Embryonic germ cells: when germ cells become stem cells. Semin. Reprod. Med. 24: 304-313.

Mueller D, Shamblott MJ, Fox HE, et al. 2005. Transplanted human embryonic germ cell-derived neural stem cells replace neurons and oligodendrocytes in the forebrain of neonatal mice with excitotoxic brain damage. J. Neurosci. Res. 82: 592-608.

Sterneckert JL, Hill CM, Palmer R, Gearhart JD. 2005. Bone morphogenetic proteins produced by cells within embryoid bodies inhibit ventral directed differentiation by Sonic Hedgehog. Cloning Stem Cells 7: 27-34.

Wilmut I, West MD, Lanza RP, et al. 2005. Human embryonic stem cells. Science 310: 1903.

Warren Sherman

Sherman W, Martens TP, Viles-Gonzalez JF, Siminiak T. 2006. Catherter-based delivery of cells to the heart. Nat. Clin. Pract. Cardiovasc. Med. 3 Suppl. 1: S57-S64.

Amit N. Patel

Adusumilli PS, Tuorto S, Patel AN. 2006. Stem cells: science and society. Natl. Med. J. India. 19: 47-48.

Patel AN, Geffner L, Vina RF, et al. 2005. Surgical treatment for congestive heart failure with autologous adult stem cell transplantation: a prospective randomized study. J. Thorac. Cardiovasc. Surg. 130: 1631-1638.

Shepler SA, Patel AN. 2007. Cardiac cell therapy: a treatment option for cardiomyopathy. Crit. Care Nurs. Q. 30: 74-80.

Kenneth Chien

Cai C-L, Liang X, Shi Y, et al. 2003. Isl1 identifies a cardiac progenitor population that proliferates prior to differentiation and contributes a majority of cells to the heart. Dev. Cell 5: 877-889.

Chien KR, 2006. Making a play at regrowing hearts. The Scientist (August). Full Text

Laugwitz K-L, Moretti A, Lam J, et al., 2005. Postnatal isl1⁺ cardioblasts enter fully differentiated cardiomyocyte lineages. Nature 433: 647-653.

Chien KR, Karsenty G. 2005. Longevity and lineages: toward the integrative biology of degenerative diseases in heart, muscle, and bone. Cell 120: 533-544.

Moretti A, Caron L, Nakano A, et al. 2006. Multipotent embryonic isl1⁺ progenitor cells lead to cardiac, smooth muscle, and endothelial cell diversification. Cell 127: 1151-1165.

Shahin Rafii

Bernardi R, Guernah I, Grisendi S, et al. 2006. PML inhibits HIF-1α translation and neoangiogenesis through repression of mTOR. Nature 442: 779-785.

Jin DK, Shido K, Kopp HG, et al. 2006. Cytokine-mediated deployment of SDF-1 induces revascularization through recruitment of CXCR4⁺ hemangiocytes. Nat. Med. 12: 557-567.

Kaplan RN, Riba RD, Zacharoulis S, et al. 2005. VEGFR1-positive haematopoietic bone marrow progenitors initiate the pre-metastatic niche. Nature 438: 820-827.

Kopp HG, Hooper AT, Broekman MJ, et al. 2006. Thrombospondins deployed by thrombopoietic cells determine angiogenic switch and extent of revascularization. J. Clin. Invest. 116: 3277-3291. Full Text

Ruan J, Hyjek E, Kermani P, et al. 2006. Magnitude of stromal hemangiogenesis correlates with histologic subtype of non-Hodgkin's lymphoma. Clin. Cancer Res. 12: 5622-5631.

Konrad Hochedlinger

Hochedlinger K, Jaenisch R. 2006. Nuclear reprogramming and pluripotency. Nature 441: 1061-1067.

Hochedlinger K, Yamada Y, Beard C, Jaenisch R. 2005. Ectopic expression of Oct-4 blocks progenitor-cell differentiation and causes dysplasia in epithelial tissues. Cell 121: 465-477.

Jaenisch R, Hochedlinger K, Eggan K. 2005. Nuclear cloning, epigenetic reprogramming, and cellular differentiation. Novartis Found. Symp. 265: 107-118.

Takahashi K, Yamanaka S. 2006. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 126: 663-676.

Elaine Fuchs

Blanpain C, Lowry WE, Geoghegan A, et al. 2004. Self-renewal, multipotency, and the existence of two cell populations with an epithelial stem cell niche. Cell 118: 635-648. Full Text

Blanpain C, Lowry WE, Pasolli HA, Fuchs E. 2006. Canonical notch signaling functions as a commitment switch in the epidermal lineage. Genes Dev. 20: 3022-3035.

Lechler T, Fuchs E. 2005. Asymmetric cell divisions promote stratification and differentiation of mammalian skin. Nature 437: 275-280. Full Text

Lowry WE, Blanpain C, Nowak JA, et al. 2005. Defining the impact of beta-catenin/Tcf transactivation on epithelial stem cells. Genes Dev. 19: 1596-1611. Full Text

Morris RJ, Liu Y, Marles L, et al. 2004. Capturing and profiling adult hair follicle stem cells. Nat. Biotechnol. 22: 411-417.

Nguyen H, Rendl M, Fuchs E. 2006. Tcf3 governs stem cell features and represses cell fate determination in skin. Cell 127: 171-183.

Rhee H, Polak L, Fuchs E. 2006. Lhx2 maintains stem cell character in hair follicles. Science 312: 1946-1949.

Tumbar T, Guasch G, Greco V, et al. 2004. Defining the epithelial stem cell niche in skin. Science 303: 359-363.

Lorenz Studer

Ban J, Bonifazi P, Pinato G, et al. 2006. ES-derived neurons form functional networks in vitro. Stem Cells Nov 16; [Epub ahead of print]

Barberi T, Studer L. 2006. Mesenchymal cells. Methods Enzymol. 418: 194-208.

Barberi T, Willis LM, Socci ND, Studer L. 2005. Derivation of multipotent mesenchymal precursors from human embryonic stem cells. PLoS Med. 2: e161. Full Text

Ferrari D, Sanchez-Pernaute R, Lee H, et al. 2006. Transplanted dopamine neurons derived from primate ES cells preferentially innervate DARPP-32 striatal progenitors within the graft. Eur. J. Neurosci. 24: 1885-1896.

Sanchez-Pernaute R, Studer L, Ferrari D, et al. 2005. Long-term survival of dopamine neurons derived from parthenogenetic primate embryonic stem cells (cyno-1) after transplantation. Stem Cells 23: 914-922. Full Text

Tabar V, Panagiotakos G, Greenberg ED, et al. 2005. Migration and differentiation of neural precursors derived from human embryonic stem cells in the rat brain. Nat. Biotechnol. 23: 601-606.

Tomishima MJ, Hadjantonakis AK, Gong S, Studer L. 2007. Production of Green Fluorescent Protein Transgenic Embryonic Stem Cells Using the GENSAT Bacterial Artificial Chromosome Library. Stem Cells 25: 39-45.

Hynek Wichterle

Dasen JS, Tice BC, Brenner-Morton S, Jessell TM. 2005. A Hox regulatory network establishes motor neuron pool identity and target-muscle connectivity. Cell 123: 477-491.

Liem KF Jr, Tremml G, Jessell T. 1997. A role for the roof plate and its resident TGFβ-related proteins in neuronal patterning in the dorsal spinal cord. Cell 91: 127-138. Full Text

Liu JP, Laufer E, Jessell T. 2001. Assigning the positional identity of spinal motor neurons: rostrocaudal patterning of Hox-c expression by FGFs, Gdf11, and retinoids. Neuron 32: 997-1012.

Roelink H, Augsburger A, Heemskerk J, et al. 1994. Floor plate and motor neuron induction by vhh-1, a vertebrate homolog of hedgehog expressed by the notochord. Cell 76: 761-775. Full Text

Hongjun Song

Barkho BZ, Song H, Aimone JB, et cl. 2006. Identification of astrocyte-expressed factors that modulate neural stem/progenitor cell differentiation. Stem Cells Dev. 15: 407-421.

Lie DC, Colamarino SA, Song HJ, et al. 2005. Wnt signalling regulates adult hippocampal neurogenesis. Nature 437: 1370-1375.

Ming GL, Song H. 2005. Adult neurogenesis in the mammalian central nervous system. Annu. Rev. Neurosci. 28: 223-250.

Owens DF, Kriegstein AR. 2002. Is there more to GABA than synaptic inhibition? Nat. Rev. Neurosci. 3: 715-727.

Song HJ, Stevens CF, Gage FH. 2002. Neural stem cells from adult hippocampus develop essential properties of functional CNS neurons. Nat. Neurosci. 5: 438-445.

Arnold Kriegstein

Kriegstein AR. 2005. Constructing circuits: neurogenesis and migration in the developing neocortex. Epilepsia 46 Suppl. 7: 15-21.

Kriegstein A, Noctor S, Martinez-Cerdeno V. 2006. Patterns of neural stem and progenitor cell division may underlie evolutionary cortical expansion. Nat. Rev. Neurosci. 7: 883-990.

Kriegstein AR, Noctor SC. 2004. Patterns of neuronal migration in the embryonic cortex. Trends Neurosci. 27: 392-399.

Martinez-Cerdeno V, Noctor SC, Kriegstein AR. 2006. The role of intermediate progenitor cells in the evolutionary expansion of the cerebral cortex. Cereb. Cortex 16 Suppl. 1: 52-61.

Conference Sponsors

Conference Organizer

The New York Stem Cell Foundation

Conference Cosponsors

Albert Einstein College of Medicine

Columbia University Medical Center

Helen and Martin Kimmel Center for Stem Cell Biology, New York University School of Medicine

The Mount Sinai School of Medicine

Tri-Institutional Stem Cell Initiative
The Rockefeller University, Memorial Sloan-Kettering Cancer Center, and Weill Medical College of Cornell University

On the evening of August 9, 2001, George W. Bush announced the first major policy decision of his presidency, on an issue that would have seemed arcane just a few years earlier: stem cells. Under the new policy, federal funding for human embryonic stem cell research would be restricted to work on 71 cell lines that the Administration had identified. The majority of these lines turned out to be useless.

What do we know about stem cells, and what can we do with them?

Founded in 2005, the New York Stem Cell Foundation (NYSCF) is a privately-funded foundation supporting human embryonic stem cell research in the search for cures of major diseases. The foundation opened the first privately-funded human embryonic stem cell laboratory in New York in March 2006 to serve as a "safe haven" where scientists from academic medical centers in the New York area and throughout the East Coast can conduct advanced human embryonic stem cell research free of the federal restrictions that—since that fateful evening in August—have limited the scope of government-supported work.

The organization's missions are: to support scientists engaged in human embryonic stem cell (hESC) research and somatic cell nuclear transfer (SCNT), through grants, fellowships and symposia; to educate the public about the importance and potential benefits of human embryonic stem cell (hESC) research and somatic cell nuclear transfer (SCNT); and to establish new collaborative, state-of-the-art research facilities supported entirely with private funds and directly focused on curing disease.

When the NYSCF held its first Translational Research Conference on October 23–24, 2006, at the Rockefeller University, the first talks provided an update on the current legal landscape of stem cell science.

For leading stem cell researchers—many of whom assembled at this historic conference—the focus was scientific rather than political. The recurring theme of the day-long conference was, exactly what do we know about stem cells, and what can we do with them? Scientists from around the world discussed the most recent findings in the most promising research areas: somatic cell nuclear transfer (SCNT), diabetes, heart disease, cancer, and neurology.

Somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a technique whereby the nucleus of a somatic cell is injected into an enucleated egg. The goal is to reprogram the DNA of the somatic cell so that it regains the ability to generate all of the cell types of the organism. Scientists working with human cells are interested in using SCNT both as a reproductive technology and as a way of producing stem cell lines, which they hope to use to replace a variety of tissues that don't regenerate on their own. The conference featured presentations highlighting the state of the art of this technique. Among the findings were the following:

• While somatic cell nuclear transfer, or "cloning" is still years away from the clinic, it is already a useful tool for researchers.
• Diseases like ALS have diverse etiology, which cloned embryonic stem cell lines can mimic in tissue culture.
• The mechanisms of egg reprogramming in early development suggest new ways to direct stem cell reprogramming in the laboratory.
• Chemical treatment may obviate the need for feeder cells in stem cell cultures.
• Nuclear transfer remains a technically challenging procedure, especially with human oocytes.

Diabetes and autoimmune disease

Some adult tissues appear to maintain stem cells that are not capable of diffentiating into every cell type, but which can regenerate a few kinds of cells. For example, the skin sheds dead cells and replaces them with new ones from a pool of adult stem cells. Other tissues do not appear to have such regenerative capacity. When the insulin-producing β cells of the pancreas are destroyed by an autoimmune reaction, for example, they are not replaced and type 1 diabetes results. Researchers are exploring a number of ways to replace β cells and investigating normal pancreatic development to inform their approach. Highlights from this session include the following:

• Autoimmune diseases like type 1 diabetes might respond well to stem cell-based therapies.
• Targeting a single gene might stimulate the pancreas to regenerate itself.
• Cultured embryonic stem cells can differentiate into pancreas-like cells, but it's unclear whether they will function in vivo.
• Researchers should be careful not to oversell the promise of stem cells in type 1 diabetes, as the field is still in its infancy.
• The number of stem cells present when the pancreas starts growing seems to determine the organ's ultimate size.

Heart disease

Researchers working on type 1 diabetes may be encouraged by reports from the world of cardiology stem cell research, where embryonic stem cells can be stimulated to differentiate into cardiomyocytes. Yet all stem cell researchers face the problem that the path from totipotent stem cell to fully differentiated cell is not clear. Some scientists are tracing the lineage of cells using fluorescent markers while others are looking for genes and growth factors that are required to commit a cell to a specific developmental pathway. Presentations at the conference indicated some recent findings showing progress in applying stem cell research to cardiology:

• A single type of stem cell, marked by the Islet-1 protein, gives rise to all of the cells in the adult heart.
• Injecting stem cells into heart tissue during bypass surgery seems to improve outcomes, but it's still unclear why.
• Scientists and surgeons are still debating whether adult bone marrow stem cells are a realistic source for heart stem cells.
• Patients who receive stem cells derived from their own bone marrow are less likely to mount immune responses against the new tissue.

Cancer research

Oncologists often see the plasticity that other scientists are trying to reproduce: tumors can dedifferentiate while stimulating new blood vessel growth to feed themselves. Researchers are very interested in understanding the mechanism by which tumor cells become pluripotent because it could lead to ways to coax other cell types to do so. Moreover, an understanding of the regulation of blood vessel growth, or angiogenesis, is critical both for the treatment of cancer, where cutting off the nutritional support for tumors is important, and for scientists trying to regenerate tissues that may have lost the supporting vascularization required for survival. Among the topics under discussion in this session were the following:

• Tumors turn back the developmental clock to adopt embryonic-like growth patterns, surprising stem cell biologists.
• Treating cultured stem cells with appropriate growth factors can stimulate angiogenesis and the formation of vascularized tissue.
• A balance between the signaling molecules Oct-4 and Cdx-2 seems to regulate stem cell reprogramming in tumors.
• The Wnt signaling pathway guides the differentiation of skin stem cells into hair follicles.

Neurology

Neuroscientists face the same challenges as other researchers trying to replace fully differentiated nonregenerating cell types. Thus, they are also studying basic stem cell biology, cell lineages, and factors required to stimulate differentiation to the appropriate cell fate. Once these difficulties are surmounted, scientists may be faced with the extraordinary complexity of restoring appropriate connections in the brain and spinal cord. The conference also included an update on recent discoveries in the effort to find ways to repair neurological damage:

• Currently available stem cell lines vary widely in their growth rates, and some labs have produced better lines than others.
• Stem cell-derived motor neurons are functional when transplanted into chick embryos.
• An emerging network of signals directs stem cells in the adult brain to become new neurons.
• Radial glial cells, long considered mere scaffolding, actually appear to direct much of the cerebrum's development.

Stem cell biologists are attempting to recapitulate development from beginning to end, and this is no easy feat. But the enormous benefits that will be reaped upon success ensure that the endeavor will not be abandoned any time soon. According to conference cochair Harold Varmus (Sloan-Kettering Institute for Cancer Research), "These technologies lead to results that already both overturn long-held dogma in the field and present a number of incredibly complicated issues." The NYSCF will be among those seeking to resolve those issues as the science advances.

Speakers:
Kevin Eggan, Harvard University
Renee Reijo Pera, University of California, San Francisco
Ali Brivanlou, The Rockefeller University
Alison Murdoch, Newcastle Fertility Centre at Life

Send in the products of somatic cell nuclear transfer

Clone. To the average person on the street, the word conjures a bizarre montage of fact and fiction, from Dolly the sheep grazing in a Scottish field to Huxleyesque farms of sterile baby incubators waiting to be harvested. To researchers, cloning is far more mundane. It is a generic term that can mean cutting and splicing DNA, isolating pure cultures of an organism, screening whole genomes for specific genes, or transferring nuclei from one cell type to another.

The two interpretations overlap at somatic cell nuclear transfer (SCNT), the correct term for the procedure that produced Dolly, the "clone" generated from a six-year-old ewe at the Roslin Institute in 1996. Transferring the nucleus of a somatic cell, like a skin cell, into an enucleated egg, then "reprogramming" the nucleus to restart the developmental script from the beginning, can produce an embryo—and subsequently an adult animal—that is genetically identical to the skin cell donor.

In principle, SCNT could yield everything from self-regenerating populations of nerve cells for treating debilitating diseases to new reproductive technologies for infertile couples. In practice, SCNT remains an exceedingly difficult technique that is still years away from application in the clinic.

Creating in vitro models of neuronal disease with SCNT

Kevin Eggan (Harvard University) discussed his efforts to use SCNT to develop new model systems for amyotrophic lateral sclerosis (ALS). ALS, also known as Lou Gehrig's disease, is a fatal neurodegenerative condition that strikes patients in the prime of their lives.

While about 10% of ALS cases are hereditary, the other 90% appear to arise spontaneously. Eggan hopes to use SCNT to reproduce this diverse etiology, by transplanting nuclei from somatic cells of ALS patients into donor oocytes. Growing the oocytes into blastocysts, then stimulating the resulting embryonic stem cells to become neurons, should yield custom-built in vitro models of each patient's disease.

Custom models of each patient's disease will speed ALS research.

To test the strategy, Eggan and his colleagues started with an existing mouse model of ALS. About 2% of ALS cases stem from a mutation in the superoxide dismutase gene, and mice carrying this mutation in a transgene develop ALS-like pathology. The researchers crossed these mice with a strain that expresses the green fluorescent protein in motor neurons. They derived embryonic stem cells from the hybrids, then stimulated the stem cells to differentiate into neurons. As the neurons differentiate, they begin to glow green, allowing the researchers to track the cells' fates in tissue culture.

The scientists can keep the resulting neurons alive for more than two months, but the cells do not grow as well as wild-type controls. Interestingly, superoxide dismutase forms aggregates in the mutant cells, just as it does in the motor neurons of humans with ALS, suggesting that the model is indeed mimicking the disease.

"I think it's an encouraging start. We're only just beginning to look at these phenotypes in culture, but I think it's fair to say that we can recapitulate some of the histopathological phenotypes that are seen in ALS in these cells," says Eggan.

Changes in gene expression upon nuclear reprogramming

Renee Reijo (University of California, San Francisco) began her talk at the beginning, with a review of the first steps in embryonic development. Immediately after fertilization, a human egg must reprogram itself to start transcribing the genes necessary for embryo formation. At the same time, it must absorb the new DNA donated by the sperm, and reprogram it as well.

"The whole object of the first few days of life is to reprogram the nuclei of the oocyte and the sperm to that of an embryo," says Reijo, "so reprogramming is a very natural function of the oocyte."

That's an important point for researchers working on SCNT, where reprogramming the donor nucleus is a critical hurdle. Probing the natural version of the process, Reijo and her colleagues used microarrays to compare gene expression patterns between eggs and early embryos. They found that the total amount of RNA decreases dramatically over the first three days of development, corresponding to a vast downregulation of oocyte RNA expression, followed by an increase in embryonic RNA expression.

The same pattern occurs even in embryos that have arrested their development at the four-cell stage. Embryonic arrest is a major cause of fertility treatment failure in the clinic, so the researchers are now trying to determine which post-reprogramming step is causing the arrest.

Weaning stem cells from their feeders

Ali Brivanlou (The Rockefeller University) took the discussion on a slight digression from SCNT to discuss an important related issue: what is the essence of "stemness?" The question is not as mystical as it sounds. From the laboratory to the Senate floor, precisely defining the characteristics of a stem cell is a tricky problem.

As a working definition, most researchers say that a stem cell is a cell capable of reproducing itself, and also producing descendants that can differentiate into other cell types. However, many of the stem cell lines used in research labs must grow alongside "feeder cells" to remain self-renewing and undifferentiated, suggesting that they lack some characteristics of true embryonic stem cells.

To study the issue, Brivanlou and his colleagues derived a new line of stem cells. Video microscopy showed that the new cells form colonies with their feeders, and cells constantly migrate in and out of the colonies. The rapid turnover makes interesting television, but complicates the research. "It's impossible to dissect the function of human stem cells when they are contaminated with this kind of background," says Brivanlou.

Moving quickly through an impressive body of additional work, Brivanlou summarized his group's subsequent findings with the new cell line. In one major breakthrough, the researchers discovered that a pigment compound originally isolated from snails, 6-bromoindirubin-3′-oxime, allows the new stem cells to grow in the absence of feeder cells. When cultured this way, the cells show substantially less migration in and out of their colonies, suggesting that the movements were actually a product of being co-cultured with feeder cells.

"I would conclude very simply that most of these effects are due to the artifact of co-culture between mouse and human cells and [have] nothing to do with the ability of a human cell to behave," says Brivanlou.

Technical challenges of SCNT

Alison Murdoch, (Newcastle Fertility Centre at Life) the final speaker of the group, addressed the difficult technical realities of SCNT. Though the public perceives it as brand-new science, the history of SCNT actually dates back to 1952, when researchers successfully "cloned" frogs with the technique. That work proved the totipotency of stem cells—their ability to produce all types of tissue.

SCNT has been undergoing a renaissance, but the underlying methods remain extremely difficult.

SCNT has been undergoing a renaissance since the 1990s, but the underlying methods remain extremely difficult. Even the first step, removing the nucleus of an egg cell while leaving the rest of the egg intact, requires substantial technical skill. Other challenges include scanty information about the timing and mechanisms of egg reprogramming, and the possibility that common methods like fluorescence microscopy could damage the cell's DNA.

"It's complicated, the science, and I think we sometimes give the impression to laypeople that it's easier than it is," says Murdoch.

When working with human eggs, researchers also have difficulty getting enough starting material. Compared to common embryological models like frog eggs, "human eggs are not only very difficult to get hold of, but they're also very small to handle," says Murdoch, whose research focuses on both assisted reproduction and other therapeutic uses of human SCNT.

Despite these challenges, Murdoch and her colleagues recently succeeded in deriving human blastocysts after transferring somatic cell nuclei into donated oocytes. The procedure's success rate is still only 10%–30%, but the team is striving to improve that.

Pointing to a continuous series of advances since the 1978 birth of Louise Brown, the first "test tube baby," Murdoch urges both researchers and policymakers not to shortchange SCNT: "If we don't go ahead and do this work now, I think it's the next generation that will chastise us."

Speakers:
Allen Spiegel, Albert Einstein College of Medicine
Gordon Keller, Mount Sinai School of Medicine
Domenico Accili, Columbia University
Douglas Melton, Harvard University

A body divided

A carpenter hammers his thumb on Monday, and by Friday the bruise has healed. An alcoholic goes on the wagon, and her liver starts to repair itself immediately. A child develops an allergy, but later becomes tolerized to the allergen.

The body's capacity for regeneration and recovery is often astonishing. Unfortunately, it is also uneven. The carpenter who amputates his thumb rather than hammering it will not grow a new one. Liver damage may heal, but brain damage may not. And while the immune system usually limits the occasional overreaction, sometimes it doesn't.

Type 1 diabetes is the medical equivalent of a perfect storm.

In type 1 diabetes, two major flaws in the body's healing systems align, forming the medical equivalent of a perfect storm. In response to a still-unknown trigger, some people mount an aggressive immune response against the insulin-secreting β cells of the pancreas. Usually striking in childhood, this autoimmune assault destroys its victims' ability to regulate their blood sugar levels. The pancreas is a particularly unfortunate target for such an attack, as it has essentially no ability to regenerate itself. Once the β cells are gone, they don't come back, and the disease's long-term sequellae can range from limb loss to coma to death.

The pancreas grows from stem cells during embryo development, so with the right type of stem cells and the right environment, it should be possible to regenerate the beleaguered pancreas of a type 1 diabetes patient.

Diverse approaches to regenerating β cells

Before delving into current research, Allen Spiegel (Albert Einstein College of Medicine) began with a brief history of diabetes therapy. The original treatment for the disease was starvation, which prevents diabetic crisis but has the unfortunate side effect of killing the patient. Insulin therapy, developed by Frederick Banting in 1922, revolutionized diabetes treatment but still failed to cure the disease.

Attacking a problem he describes as "harder than rocket science," Spiegel and his colleagues are searching for ways to stimulate the regeneration of β cells. So far, the team has found at least three promising strategies. First, precursor cells in the pancreas can exhibit β cell-like insulin responses under the right conditions, so it might be possible to stimulate the precursor cells to replace the missing β cells functionally. Second, Spiegel suggests that specific immunosuppression could help preserve remaining β cells before the patient's immune system has a chance to eradicate them. Third, the scientists have discovered that in mice, disrupting a single gene, called Men1, can lead to pancreatic cell proliferation. If that finding holds true in humans, MEN1-targeting drugs or gene therapy might help regenerate the pancreas.

Gordon Keller (Mount Sinai School of Medicine) put the subject into embryological context. The pancreas normally grows from the embryonic endoderm, a tissue produced during gastrulation, or formation of the gut. Keller and his colleagues hope to approximate gastrulation in vitro to generate pancreatic cells.

With careful manipulation, embryonic stem cells can yield pancreas-like cells.

Under the right conditions, mouse embryonic stem cells will form "embryoid bodies" in culture dishes, and the researchers used this system to identify some of the signaling pathways required for gastrulation. With careful manipulation, the cultures can yield hepatocytes, as well as some pancreatic-like cells on the margins of the hepatocyte colonies. Encouragingly, the cultured hepatocytes can occasionally become functional liver cells when transplanted into animals. The team is now testing the process in human stem cell lines.

Domenico Accili (Columbia University) shifted the focus to the concerns of diabetes patients, many of whom were in the audience. Insulin therapy was a definitive medical breakthrough, turning a death sentence into a manageable disease. Accili says that while stem cells have substantial promise, patients should not expect another giant leap anytime soon.

Reviewing recent advances like the Edmonton protocol for pancreatic cell transplantation, and efforts to generate β cells in vitro, he concludes that there is no way to predict which, if any, of the current crop of projects will yield treatments. That's a good reason to avoid premature optimism, but also a good reason to pursue further research.

Development and redevelopment of the pancreas

Doug Melton (Harvard University) departed from the broad generalities of a typical keynote presentation to delve directly into new data. In his laboratory's type 1 diabetes work, the focus is on how solid organs, especially the pancreas, regulate their development.

The team uses mice lacking the Pdx1 gene as their primary model system. The developing pancreas normally expresses Pdx1, and animals without functional Pdx1 lack pancreases. Injecting wild-type embryonic stem cells into these mice causes them to grow pancreases, but the size of the organ depends on the number of injected cells. That suggests that the pancreas has an intrinsic size limit determined by the number of starting cells.

The number of starting stem cells may determine pancreas size.

Reversing the experiment, the scientists generated a mouse strain in which the Pdx1 promoter drives an inducible toxin gene system. Feeding a chemical inducer to these mice kills any developing pancreatic cells, but does not kill fully developed pancreatic cells. If pregnant mice receive the inducer when their embryos are between 9 and 10 days old, the resulting pups have underdeveloped pancreases. Feeding the inducer at day 11 or later has no effect on the organ's size, suggesting that once the pancreas is developed, it no longer contains any stem cells that could regenerate the organ.

Searching for ways to stimulate pancreatic regeneration that do not require preexisting pancreatic stem cells, Melton and his colleagues are now using "high-throughput screening," a procedure common in the pharmaceutical industry but rare in basic research. After adapting the technology to their unique experimental system, the team is now screening thousands of genes in embryonic stem cells to find those that induce pancreatic growth during development.

While it will likely be years before the work leads to usable treatments, Melton is optimistic. "We haven't learned anything that leads us to believe that this is not a solvable problem," he says.

John Gearhart, Johns Hopkins University
Kenneth Chien, Harvard Medical School
Warren Sherman, Columbia University
Amit Patel, University of Pittsburgh

A heart-fixing job of staggering complexity

Our minds tell us, perhaps a bit self-servingly, that the most important organ in the body is the brain. Nonetheless, humans have realized for millennia that the hardworking, essential, and fragile heart also deserves special treatment. Serious brain damage can be debilitating, but serious heart damage is instantly lethal.

The heart has a formidable capacity to repair itself.

Considering its pedestrian function—it's just a pump, after all—the heart has proven surprisingly difficult to repair, and virtually impossible to replace. When coronary arteries clog, radiologists can scrape them out and surgeons can bypass them, but the long-term damage from lost blood flow, or ischemia, often persists. Meanwhile, engineers have designed hundreds of ingenious heart prosthetics, from pacemakers to replacement valves to artificial hearts, but their uses are still limited by infections and immune responses, as well as the malfunctions and ordinary wear that affect all machines.

Fortunately, the heart has a formidable capacity to repair itself, if the patient can be kept alive long enough. Researchers attempting to speed the heart's healing have long hoped that stem cells would be the answer, and the early results have been tantalizing. When scientists remove exogenous growth factors and leave cultured embryonic stem cells to their own devices, the petri dish soon grows different types of embryonic tissue, including cardiomyocytes that start pulsating spontaneously.

A beating cluster of cells is a long way from a replacement heart, but the gap between the laboratory and the clinic seems to be narrowing.

Purifying cardiac stem cells for treatment of heart disease

Reviewing the literature on stem cells in heart disease, John Gearhart (Johns Hopkins University) found more than 40 studies in which scientists had used stem cells to repair heart damage in patients. In every study, the stem cells improved heart function at least somewhat, even though the experimental designs, conditions, outcome measures, and stem cell sources were different in each study. Everything seems to work a little bit. While that's encouraging, it provides few clues to the underlying mechanisms of cardiac regeneration.

"All of these different cell sources have been used, [so] when you actually then look at the outcome measures, you don't really know what this improvement is due to," says Gearhart.

A new line of heart stem cells can yield working heart cells.

One major problem is that the stem cells the patients have received have been mixed populations, with multiple cell types that could be contributing to the outcome. To get around that, Gearhart and his colleagues went back to tissue culture, and created an embryonic stem cell line in which a cardiac-specific gene promoter drives a green fluorescent protein (GFP) gene. GFP glows green under ultraviolet light, so as the stem cells differentiated, the investigators could separate them with a cell sorter and isolate only the cardiac cells. Testing these, they purified a line of heart stem cells that can regenerate themselves and also give rise to working heart cells.

In a mouse model of cardiac infarction, grafting the newly isolated stem cells into the heart improves cardiac output. The researchers are now testing the new cell line in the clinic, and also trying to characterize the genes involved in cardiomyocyte differentiation.

Lineage analysis of cardiac cells

Kenneth Chien (Harvard Medical School) and his colleagues are also searching for heart stem cells, by tracing cell lineages in developing mouse hearts. Chien reasoned that if the heart is like the blood, in which all cell types come from a single type of progenitor cell, then tracing heart cell lineages should lead directly to a cardiac stem cell. He was right.

To make a heart, a developing embryo has to direct the formation of three types of tissues: endothelium, smooth muscle, and cardiac muscle. "In other words there's a branch point, where sometime in development in the embryo ... this decision is made," says Chien. Cells that are committed to being cardiac tissue, but have not decided what specific cell type they will form, could be clinically useful cardiac stem cells.

Tracing the lineages of murine heart cells during development, the investigators found that a protein marker called Islet-1 flags exactly the cells they were seeking. "Smooth muscle cells, endothelial cells, and conduction system cells ... are actually derived from Islet precursors, so at some point in time Islet is the common denominator for all these lineages," says Chien.

Can bone marrow-derived stem cells work in the heart?

The session also featured comments from two sides of an ongoing controversy, in response to a pair of articles published two weeks earlier. In the articles, different teams of researchers described the results of treating heart disease with adult bone marrow-derived stem cells. One team saw positive results, the other negative, and surgeons and stem cell scientists are now lining up on both sides of the issue. Chien emphasized the negative results, saying that the apparent failure of adult stem cells in this application highlights the need for further research on embryonic stem cells.

Warren Sherman (Columbia University), who spoke after Chien, thinks otherwise. "The story is not over in my opinion, and I think it would be a mistake for us to abandon any initial effort ... prematurely," says Sherman, a surgeon who specializes in post-ischemic heart disease.

Post-ischemic disease, a common condition within the umbrella category of "heart disease," is what happens after a patient loses blood flow to a portion of the heart. In recent years, surgeons have tried to heal post-ischemic disease by injecting the affected areas of the heart with stem cells from various sources, including bone marrow-derived, adipose-derived, and fetal cells. The theory is that the right type of stem cells will differentiate into cardiac muscle to repair the post-ischemic damage, but the results have been ambiguous. The controversial pair of recent papers was a continuation of this strategy, using a subpopulation of bone marrow-derived stem cells expressing the CD34 protein. Those cells had looked promising in preclinical studies, but the clinical results were less impressive.

However, the lackluster results in humans could be a product of the trial design. In the earlier preclinical studies, researchers induced myocardial infarctions in rats, then injected more than 3000 stem cells per gram of tissue into the animals' hearts. In the human trials, patients received a much smaller dose of cells relative to the amount of heart tissue. "At best, when we translated [these] preclinical data into the clinical domain, we fell at least a power of ten short in terms of what might work," says Sherman.

Amit Patel (University of Pittsburgh) also believes that adult stem cells are a promising tool for treating heart disease, and points out that they have some advantages over embryonic or fetal cells. For example, adult cells can be derived from the patient, eliminating the risk of an immune response against the injected cells. "No matter how positive the potential outcomes are, we still have to deal with our own immune systems," says Patel.

To avoid that problem, Patel and his colleagues took bone marrow from patients undergoing heart bypass surgery, quickly isolated stem cells, and sent the cells back to the operating room. With the patient still on the table, surgeons then injected the cells into the ischemic areas of the heart that they were unable to repair with bypasses. By several measures, patients who received this treatment fared better than controls who received only the bypass operation.

The researchers are testing similar autologous stem cell strategies in patients with other types of heart disease, and while the results are promising, Patel cautions that the strategy is not a panacea. "For every 100 patients that get screened for one of these trials, 5% qualify," he says, adding that "this is not something that's just globally applicable to all patients."

The panel discussion at the end of the session echoed Patel's cautionary tone. In other words, while the potential of cardiac stem cells is heartwarming, we should be careful not to lose our heads.

Speakers:
Shahin Rafii, Weill-Cornell Medical College
Konrad Hochedlinger, Harvard Medical School
Elaine Fuchs, The Rockefeller University

From regression to remission

During development, the cells in an embryo carry out a long series of rapid, carefully controlled divisions and specializations. A fertilized egg divides into two cells, then four, then eight, and so on, each cell retaining the potential to create all of the tissues in an adult. These are totipotent stem cells.

As a tumor grows, oncology recapitulates ontogeny.

As development proceeds, the dividing cells progressively narrow their options, first committing to form general tissue types, then specific subtypes. In the process, they lose their totipotency. At birth, most of an individual's cells have become terminally differentiated, ready to serve out their hyperspecialized lives before being replaced by duplicates.

In cancer, the process partially reverses. Rather than succumb to its proper fate, a differentiated cell divides, generating a tumor. As the tumor grows, it often regains hallmarks of embryonic tissue; oncology recapitulates ontogeny. That makes cancer doubly interesting to biomedical researchers: as a disease in need of new treatments, and as a model system for studying the behavior of stem cells.

Rebuilding the vasculature

Shahin Rafii (Weill-Cornell Medical College) discussed his work on one of the hottest topics in cancer research: angiogenesis, or the development of new blood vessels. When a tumor grows larger than a few millimeters in diameter, it must recruit its own blood supply, or the interior cells will die. While oncologists want to stop angiogenesis, clinicians using stem cell-based therapies will need to start it—both need more information about how the process works.

"If the vascular system is not reconstructed, none of the translational stem cell therapy is going to work," says Rafii, adding that no matter how many stem cells researchers transplant into a patient, "if there [are] no stabilized vessels, that newly formed tissue is going to collapse."

To stabilize newly generated blood vessels, a developing organ, stem cell transplant, or tumor needs to recruit perivascular cells to surround and support the vessels. By culturing a population of human fetal liver cells with appropriate growth factors, Rafii and his colleagues managed to replicate this process, training the cells to form stable vascularized tissue when transplanted into the ear of an immunocompromised mouse. Using similar techniques, the team has also produced functional, vascularized heart muscle tissue from human embryonic stem cells.

The investigators also found that blocking the growth of endothelium prevents muscle tissue growth, underscoring Rafii's argument that angiogenesis is essential for tissue or organ regeneration. The researchers are now searching for the specific molecular signals that coordinate tissue growth with blood vessel stabilization.

Stimulating proper differentiation of stem cells

Konrad Hochedlinger (Harvard Medical School) explained how he uses cancer as a model system for studying stem cell biology. For most types of stem cell therapies to work, researchers need to be able to reprogram the nucleus of a partially or fully differentiated cell, turning back the developmental clock to the time when the cell was pluripotent. Currently, cells can be reprogrammed in the laboratory with a handful of techniques, including somatic cell nuclear transfer, explantation of the cells from live tissue into tissue culture, and fusion of somatic cells with established embryonic stem cell lines. Each approach has its own serious drawbacks, and none works reliably.

Oct-4 and Cdx-2 are two of the factors regulating reprogramming.

A better strategy would be to reprogram the cells by exposing them to specific transcription factors, something tumors do routinely. To find out how, Hochedlinger and his colleagues started with a short list of factors that can stimulate cultured fibroblasts to adopt a stem cell-like phenotype. The researchers created a transgenic mouse in which they could induce the expression of one of these factors, called Oct-4, at any time.

Inducing Oct-4 expression in a mouse appears to stimulate existing stem cells to proliferate, while inhibiting cell differentiation, causing tumors in the animal's gut and skin. Oct-4 expression is inversely proportional to the expression of another factor, Cdx-2. Knocking down Cdx-2 expression with inhibitory RNA during embryonic development also causes tumors in the intestine, but inhibiting Cdx-2 in adult animals has no effect, so the gene is only required for cell programming in a specific period of development. The scientists are now using their mouse systems to pinpoint additional factors that control reprogramming.

Elaine Fuchs (The Rockefeller University) concluded the session with a brisk presentation that got under the skin—which, it turns out, is an excellent place to study both stem cells and cancer. Skin cancer is the most prevalent type of cancer, and skin itself is "a readily accessible tissue, its lineages are spatially and temporally defined," Fuchs explained. "Adult skin stem cells ... are in fact able to propagate in culture, and they do have clinical potential."

In mammals, the descendants of stem cells in the lowest layer of the skin specialize as they move to the surface, forming the protective barrier of the epidermis as well as more complex structures, such as sweat glands and hair follicles. The Wnt signaling pathway regulates this process; mice with a disrupted Wnt pathway become inordinately furry, and also develop hairball-like skin tumors called pilotricomas.

Looking at downstream targets and effects of Wnt, Fuchs and her colleagues are now identifying the signals responsible for switching skin cells onto specific developmental tracks. "We're beginning to understand the earliest processes by which multipotent cells commit to taking one path or another path," says Fuchs. The researchers hope to use that understanding to develop skin grafts with hair follicles and sweat glands, which current grafts lack.

Some of the underlying processes in skin cell programming are broadly conserved across different species and cell types, so learning how to reprogram skin stem cells could illuminate ways to reprogram other cell types. Skin, it seems, is more than skin deep.

Speakers:
Lorenz Studer, Memorial Sloan-Kettering Cancer Center
Hynek Wichterle, Columbia University
Hongjun Song, Johns Hopkins University
Arnold Kriegstein, University of California, San Francisco

Brain teasers

Neurology is the poster child of stem cell research. The promise of treating conditions like paralysis, amyotrophic lateral sclerosis, and Parkinson's disease prompts celebrities to testify before Congress, medical activists to organize lobbying campaigns, and companies to build entire research facilities.

Even the embryonic stem cells themselves seem to favor neurological applications. "For peculiar and curious reasons, stem cells have a predeliction to undergo pathways of neural differentiation," explains Thomas Jessell, who chaired the session on neurology.

Stem cells like to become neurons.

Better still, some neuronal cells maintain their multipotency all the way into adulthood, holding out the promise that researchers might be able to dodge the ethical and immunological challenges of using embryonic cells. "In the nervous system ... it's become progressively more established that there are adult neural stem cells in certain privileged areas," says Jessell.

But that's where the good news ends. To turn laboratory findings into clinical treatments, researchers need to produce specific kinds of cells, and there are dozens of types to choose from in the brain. Reversing paralysis may call for new motor neurons, while curing Parkinson's disease will take dopaminergic neurons. They are not interchangeable.

Best practices for stem cell generation

Researchers are taking numerous parallel approaches, ranging from advanced preclinical studies of specific treatments to basic research on brain development, to address the need for specific neural cells.

Lorenz Studer (Memorial Sloan-Kettering Cancer Center) wants to use embryonic stem cells to treat Parkinson's disease. As a starting point for this ambitious project, he asked a simple question: How well do the available embryonic stem cell lines grow in culture? Comparing 8 lines that are approved for NIH-funded research and 14 lines derived after August 2001 (and therefore not approved), they found substantial differences in growth rates. That wasn't so surprising, but the data revealed something else that was.

"We would have thought maybe these growth rates related to [the] stochastic genetic makeup of the cells," says Studer, but "growth rates correlate not with stochastic variability but ... the lab that they were derived from." Some labs apparently derive better stem cells than others, and so far, nobody knows why.

In response, Studer and his colleagues are borrowing a technique from the drug industry, screening thousands of cell lines with different potential signaling molecules to see what factors are required for stem cell maintenance and growth.

Besides this "high-throughput screening" approach, the team is also implanting stem cell-derived dopaminergic neurons into the brains of rats with Parkinson's disease. The implanted cells appear to survive and multiply, and while they prompt some overgrowth of neurons, the researchers are optimistic that the approach could work in humans. "We are still a way from using these cells in a clinical setting, but we've made a lot of progress," says Studer.

From embryonic stem cell to motor neuron

Hynek Wichterle (Columbia University) and his colleagues are trying to generate motor neurons from embryonic stem cells. The loss of motor neurons is a hallmark of deadly and currently incurable diseases like amyotrophic lateral sclerosis and spinal muscular atrophy, but replacing these specialized neurons is a challenge. "We can ... relatively easily generate neurons from embryonic stem cells, but to go to very particular and specific subtypes of neurons can be quite tricky," says Wichterle.

To figure out how to do it, the researchers used embryonic stem cells from mice that carry a green fluorescent protein gene. Because the cells glow under ultraviolet light, they are easy to trace as they develop. Exposing the mouse cells to fibroblast growth factor and retinoic acid prompted them to differentiate into motor neurons, which were functional when transplanted into chicken embryos.

Importantly, the team also found that they could produce motor neurons adapted for more anterior or more posterior portions of the developing spinal cord, by manipulating the concentrations of retinoic acid and fibroblast growth factor. They are now using the cultured motor neurons as a model system to study nervous system development and disease.

Encouraging adult neural stem cell growth in vivo

Hongjun Song (Johns Hopkins University) noted that, "It actually took about 100 years for people to appreciate that our brains are not static, and we do have some neurons that are generated in specific regions," referring to the cells of the subventricular zone and the dentate gyrus, which sometimes can regenerate.

Outside these two specific regions, though, cell division does not normally produce new neurons, and Song and his colleagues want to know why. The researchers derived multipotent neuronal stem cells from adult rat brains, and from human brain samples taken during surgeries. These stem cells can grow new neurons in tissue culture. In rats, the cultured stem cells can grow and apparently form new synapses when transplanted into the hippocampus of the brain, but not when put into the spinal cord. Specific promoter and inhibitor signals in neuronal compartments seem to drive this bias.

Birth and development of neurons in the cerebral cortex

Arnold Kriegstein's group (University of California, San Francisco) focuses on the role of neural stem cells in the development of the cerebral cortex. Much of Kriegstein's work focuses on radial glial cells, which were thought to serve merely as a scaffolding system in the developing brain; radial glial cells grow long processes, which neurons then migrate along to reach their final destinations.

Radial glial cells are the mothers and architects of the cerebrum.

In order to track this migration, the researchers injected the radial glial cells of developing mice with a retrovirus carrying a green fluorescent protein gene. The injected cells and their descendants then glow under ultraviolet light. That's when the team got a surprise. "In fact, the radial glial cell gives rise to the neuron, and then in a sense guides the neuron to the cortex, because it migrates along the parental fiber to get to its final position," says Kriegstein.

New neurons bud from the base of the radial glial cell, then migrate along the mother cell's extended body, stacking into their final positions like cars reaching the end of a one-lane road. By changing the types of neurons they spawn at different times during development, the radial glial cells may orchestrate the formation of distinct layers in the finished brain. Rather than being mere scaffolding, the radial glial cells are both the mothers and the architects of the deep cerebral cortex.

Kriegstein suggests that a few relatively simple genetic changes in this developmental program could explain the evolution of more heavily folded cerebral cortexes, which are essential for higher reasoning. If that's correct, then radial glial cells are more than just an interesting research subject. They literally make you think.

Somatic Cell Nuclear Transfer

What molecular signals stimulate human eggs to begin blastocyst formation?

Can existing stem cell lines be weaned from their dependence on feeder cells?

Why is so much mRNA destroyed in the first three days of embryonic development?

Do stem cell-derived neurons mimic the pathogenesis of ALS accurately?

Diabetes and Autoimmune Disease

What are the genes that induce pancreatic growth during development, and can they be activated in adults with type 1 diabetes?

Will stem cells ultimately yield a breakthrough analogous to Banting's invention of insulin therapy?

Can pancreatic cells derived in tissue culture survive and function in adult animals?

What is the normal role of the Men1 gene in stimulating pancreatic development?

Heart Disease

Can Islet-1-derived stem cells yield functional new heart tissue in patients?

Is adult bone marrow a realistic source for heart stem cells?

Will autologous stem cell transplants be as useful in the general heart patient population as they appear to be in specific subsets of patients?

Cancer Research

What are the molecular signals that coordinate tissue growth with angiogenesis?

Besides Oct-4 and Cdx-2, what other factors regulate stem cell reprogramming in development?

What are the signals downstream of Wnt that switch skin cells onto specific developmental tracks?

Neurology

Will implanted dopaminergic neurons survive and function in the brains of Parkinson's disease patients?

Can stem cell-derived motor neurons function in adult mammals?

What are the signals directing the growth of new neurons from the stem cells naturally present in the adult brain?

Can a few simple mutations explain the evolution of higher reasoning?